Electronic device and method of processing user actuation of a touch-sensitive input surface

ABSTRACT

An electronic device includes a proximity-sensitive touch sensor array which extends along an input surface of the electronic device and a processing device coupled to the touch sensor array. The processing device is configured to process data captured by the touch sensor array to determine a finger angle at which a finger is directed towards the input surface and an actuation position on the input surface. The processing device is configured to establish an offset-corrected actuation position as a function of the actuation position and the finger angle.

FIELD OF THE INVENTION

The application relates to an electronic device and to a method ofprocessing user actuation of an input surface. The application relatesin particular to electronic devices which have a proximity-sensitivetouch sensor array to detect an actuation location.

BACKGROUND OF THE INVENTION

Touch screens are used in a wide variety of electronic devices. Handheldelectronic devices, such as handheld mobile communication terminals, arefrequently provided with a proximity-sensitive touch sensor array. Theelectronic device performs a function in response to an input action,which depends on the actuation position at which the user touches aninput surface of the electronic device, e.g. a window overlaid onto adisplay.

One general problem with this kind of user input interface is that theremay be a discrepancy or offset between where a user thinks he haspressed onto the input surface and the actuation position at which theuser has actually pressed onto the input surface. With increasingprocessing capabilities and functionalities provided in electronicdevices such as mobile communication terminals, the offset problem maycause the electronic device to perform an operation which is differentfrom the operation intended by the user.

SUMMARY

There is a continued need in the art for an electronic device and for amethod of processing user actuation of an input surface which addresssome of the above shortcomings. In particular, there is a continued needin the art for an electronic device and for a method of processing useractuation of an input surface in which the user input is processed so asto mitigate the risk that an operation other than the one intended bythe user is performed.

According to embodiments, a finger angle at which the finger is directedtowards an input surface of the electronic device is determined. Anoffset-correction is performed which depends on the finger angle. Forillustration, an offset having a magnitude which is set based on thefinger angle may be added to a detected actuation position on the inputsurface. Since the discrepancy between where a user thinks he haspressed onto the input surface and the actuation position at which theuser has actually pressed onto or otherwise actuated the input surfacedepends on how the finger is directed towards the input surface, thistechnique allows the electronic device to at least partially correct forthis offset.

According to embodiments, both the actuation location and the fingerangle are determined from data captured using a proximity-sensitivetouch sensor array. This allows an improved input accuracy to beattained using commodity hardware, such as a capacitive touch sensorarray, which is at any rate provided to detect the actuation position.

According to an embodiment, an electronic device is provided. Theelectronic device comprises a proximity-sensitive touch sensor arraywhich extends along an input surface of the electronic device. Theelectronic device comprises a processing device coupled to the touchsensor array and configured to process data captured by the touch sensorarray. The processing device is configured to process the data capturedby the touch sensor array to determine a finger angle at which a fingeris directed towards the input surface and an actuation position on theinput surface. The processing device is configured to establish anoffset-corrected actuation position as a function of the actuationposition and the finger angle.

The processing device may be configured to determine a variation indistance of the finger from the input surface in a spatially resolvedmanner and to derive the finger angle from the variation in distance.The variation in distance can be determined from the data captured usingthe touch sensor array.

The touch sensor array may comprise a conductive pattern for capacitivetouch and proximity sensing. The conductive pattern may be formed from atranslucent material, e.g. from Indium Tin Oxide (ITO), graphene, orother suitable materials. The conductive pattern may be attached to awindow or a separate panel member. The conductive pattern may beoverlaid onto a display. The processing device may process data whichrepresent self-capacitances or mutual capacitances of the conductivepattern to determine the finger angle.

The conductive pattern may comprise a plurality of rows and a pluralityof columns. The processing device may be configured to determine thefinger angle based on self-capacitance measurements of the plurality ofrows and self-capacitance measurements of the plurality of columns. Theprocessing device may be configured to determine the finger angle basedon both mutual capacitance measurements and self-capacitancemeasurements.

Alternatively or additionally to capacitive sensing, the touch sensorarray may be configured to use sensing techniques other than capacitivetouch and proximity sensing. For illustration, the touch sensor arraymay comprise an optic touch sensor. The touch sensor array may comprisean Infrared (IR) sensing sensor array. The touch sensor array may useelectrical fields for proximity and touch sensing. The touch sensorarray may use sonar, ultra sound and/or Doppler measurements forproximity and touch sensing.

The processing device may be configured to determine the actuationposition based on mutual capacitance measurements between rows andcolumns of the conductive pattern.

The processing device may be configured to determine the actuationposition based on the self-capacitance measurements of the plurality ofrows and of the plurality of columns.

The processing device may be configured to carry out a row scan toperform the self-capacitance measurements for the plurality of rows anda column scan to perform the self-capacitance measurements for theplurality of columns, and to derive the finger angle from data obtainedin the row scan and data obtained in the column scan.

The processing device may be configured to derive the finger angle froma spatial gradient of self-capacitance data and/or mutual capacitancedata. The processing device may be configured to compare the datacaptured in the row scan to a first plurality of spatially-dependentdata sets and to compare the data captured in the column scan to asecond plurality of spatially-dependent data sets, and to determine thefinger angle from both comparisons. Each one of the data sets may beassociated with respectively one of plural pre-defined finger angles. Aninterpolation between the different pre-defined finger angles may beperformed. Both the finger angle and a direction of a projection of thefinger onto the input surface may be derived from the data capturedusing the touch sensor array. The finger angle may be computed asweighted average of the pre-defined finger angles, with the weightingfactors depending on self-capacitance data and/or mutual capacitancedata.

The processing device may be a controller coupled to the conductivepattern. The controller may be configured to provide theoffset-corrected actuation position to an application processor of theelectronic device. The controller may be an application-specificintegrated circuit. By integrating the finger angle dependentoffset-correction into the controller of the touch sensor panel, nomodifications have to be made to the application processor(s) of theelectronic device.

The processing device may be configured to add or subtract an offset tothe actuation position on the input surface to establish theoffset-corrected actuation position.

The processing device may be configured to establish a magnitude of theoffset as a function of the finger angle. The magnitude of the offsetmay be independent on the actuation position at which the finger waspressed against the input surface. The magnitude of the offset may be adecreasing function of finger angle.

The processing device may be configured to derive a finger orientationfrom the data captured by the touch sensor array, the finger orientationdefining a direction of a projection of the finger onto the inputsurface. I.e., the finger orientation defines how the finger is orientedrelative to the in-plane coordinate axes of the input surface. Thefinger angle defines how the finger is oriented relative to the plane ofthe input surface. The processing device may be configured to establisha direction of the offset as a function of the finger orientation. Theprocessing device may be configured to establish the direction of theoffset as a function of the finger orientation and independently fromthe finger angle. The processing device may be configured to establishthe magnitude of the offset as a function of the finger angle andindependently from the finger orientation.

The touch sensor array may further comprise a force sensor configured todetermine a force with which the finger is pressed or multiple fingersare pressed against the input surface. The processing device may beconfigured to derive an offset-corrected force value from an output ofthe force sensor and the finger angle. In this way, offset problems maybe compensated at least in part also for the force which is applied bythe user. Performing offset-correction for force sensor values may beuseful in particular when the force is used as an input coordinate,sometimes also referred to as z-coordinate, in addition to oralternatively to the x and y coordinates on the input surface.

The processing device may be configured to determine finger angles forplural fingers which perform a multi-touch operation on the inputsurface. An offset-corrected actuation position may be determined foreach one of the plural fingers. Thereby, offset correction may beperformed also for multi-touch operations.

The electronic device may further comprise an application processorcoupled to the processing device to receive the offset-correctedactuation position. The application processor may be configured toperform an operation which is selected in dependence on theoffset-corrected actuation position.

The electronic device may be a handheld wireless communication terminal.The electronic device may be a handheld portable telephone, a personaldigital assistant, or a handheld computer.

Look-up tables and/or functions which are used to determine an offset independence on the determined finger angle may be stored in theelectronic device. The look-up tables and/or functions may bepre-defined data, which may be generated by sampling offsets for varioususers as a function of finger angle and processing the sampled data togenerate tables and/or functions that can be queried to determine anoffset as a function of finger angle. Alternatively or additionally, thelook-up table(s) and/or function(s) may be generated by the electronicdevice in a training phase in which the electronic device automaticallydetermines the offsets between intended and actual actuation positionsfor various finger angles. The electronic device may share the look-uptables and/or functions with other devices used by the same user. Forillustration, the electronic device may have a communication interfaceto transfer the look-up tables and/or functions to other electronicterminals and/or to a server.

The processing device may perform an offset-correction which depends onthe finger which touches the input surface and/or which depends on anorientation of the electronic device. For illustration, one of severaldifferent tables may be queried to determine the offset for a givenfinger angle, depending on which finger touches the input surface and/ordepending on device orientation. Alternatively or additionally, one ofseveral different functions may be evaluated to determine the offset fora given finger angle, depending on which finger touches the inputsurface and/or depending on device orientation.

According to an embodiment, a method of processing user actuation of aninput surface of an electronic device is provided. Data are capturedusing a proximity-sensitive touch sensor array which extends along theinput surface of the electronic device. The data captured by the touchsensor array are processed to determine a finger angle at which a fingeris directed towards the input surface and an actuation position on theinput surface. An offset-corrected actuation position is established asa function of the actuation position and the finger angle.

Further features of the method according to embodiments and the effectsattained thereby correspond to the features of the electronic devicesaccording to embodiments.

The method may be performed by the electronic device of any one aspector embodiment.

It is to be understood that the features mentioned above and featuresyet to be explained below can be used not only in the respectivecombinations indicated, but also in other combinations or in isolation,without departing from the scope of the present invention. Features ofthe above-mentioned aspects and embodiments may be combined with eachother in other embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and advantages of the inventionwill become apparent from the following detailed description when readin conjunction with the accompanying drawings, in which like referencenumerals refer to like elements.

FIG. 1 is a front view of an electronic device according to anembodiment.

FIG. 2 is a block diagram of the electronic device of FIG. 1.

FIG. 3 is a perspective view illustrating offset-correction inelectronic devices of embodiments.

FIG. 4 is a cross-sectional side view of an input surface illustratingdetermination of a finger angle.

FIG. 5 is a plan view of the input surface illustrating theoffset-correction for the finger angle of FIG. 4.

FIG. 6 is a cross-sectional side view of the input surface illustratingdetermination of another finger angle.

FIG. 7 is a plan view of the input surface illustrating theoffset-correction for the finger angle of FIG. 6.

FIG. 8 is a flow chart of a method according to an embodiment.

FIG. 9 is a flow chart of a method according to an embodiment.

FIG. 10, FIG. 11 and FIG. 12 illustrate determination of a finger angleusing a proximity-sensitive touch sensor array.

FIG. 13 is a plan view of a touch sensor panel having aproximity-sensitive touch sensor array.

FIG. 14 is a flow chart of a method according to an embodiment.

FIG. 15 and FIG. 16 show self-capacitance values obtained in a row scanand column scan for different finger angles.

FIG. 17 is a flow chart of a method according to an embodiment.

FIG. 18 is a flow chart illustrating a procedure of training anelectronic device according to an embodiment.

FIG. 19 illustrates a communication system comprising at least oneelectronic device according to an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, embodiments of the invention will be described indetail with reference to the accompanying drawings. It is to beunderstood that the following description of embodiments is not to betaken in a limiting sense. The scope of the invention is not intended tobe limited by the embodiments described hereinafter or by the drawings,which are taken to be illustrative for embodiments. The features of thevarious embodiments may be combined with each other, unless specificallynoted otherwise.

The drawings are to be regarded as being schematic representations, andelements illustrated in the drawings are not necessarily shown to scale.Rather, the various elements are represented such that their functionand general purpose become apparent to a person skilled in the art. Anyconnection or coupling between functional blocks, devices, components orother physical or functional units shown in the drawings or describedherein may also be implemented by an indirect connection or coupling.Functional blocks may be implemented in hardware, firmware, software ora combination thereof. While electronic devices of an embodiment may bewireless communication devices such as cellular telephones, personaldigital assistants, or other handheld devices having communicationcapabilities, the input interface is not limited to being used in suchhandheld communication devices.

Electronic devices having an input interface will be described. Theinput interface comprises a proximity-sensitive touch sensor array. Aprocessing device is coupled to the proximity-sensitive touch sensorarray and is configured to determine not only an actuation position,e.g. a touch position, but also a finger angle from data captured by thetouch sensor array. The finger angle defines at which angle the fingeris directed towards an input surface. The finger angle may be defined asthe angle between a longitudinal axis of the finger and the inputsurface or as the angle between a lower side of the finger and the inputsurface. The processing device performs an offset correction whichdepends on the finger angle. An offset may be added to the actuationposition to establish an offset-corrected actuation location, with themagnitude of the offset being determined as a function of the fingerangle. The magnitude of the offset may decrease with increasing fingerangle.

FIG. 1 is a front view of a handheld electronic device 1 and FIG. 2 is aschematic block diagram representation of the handheld electronic device1. The handheld electronic device 1 has an input interface. The inputinterface includes a proximity-sensitive touch sensor array which mayextend along an input surface 3. The input surface may be defined by awindow which is overlaid onto a display. The input interface maycomprise a display, thereby implementing a touch-sensitive screen. Thehandheld electronic device 1 has a processing device 4 coupled to theinput interface. The processing device 4 may comprise an applicationspecific integrated circuit and/or one or plural processors. Forillustration, the functions of the processing device 4 described belowmay be performed by a controller 12 of a touch sensor panel.Alternatively or additionally, the functions of the processing device 4described below may also be performed by an application processor 11 ofthe handheld electronic device 1. The processing device 4 may beconfigured such that, at least in some modes of operation, it determinesan offset-corrected actuation location by processing data captured bythe proximity-sensitive touch sensor array. The processing device 4 maydetermine how the distance between the finger and the input surfacevaries as a function of position. The processing device 4 may determinea finger angle from the data captured by the proximity-sensitive touchsensor array. The processing device 4 may add an offset to the sensedactuation position or may subtract an offset from the sensed actuationposition, with the offset being selected as a function of the fingerangle. The offset may be determined using a look-up table and/or byevaluating a function which quantifies the offset between the positionwhere a user thinks he has touched the input surface and the actualactuation position, as a function of finger angle. By adding this offsetto the sensed actuation position, at least part of the discrepancybetween the position where a user thinks he has touched the inputsurface and the actual actuation position may be compensated. Theprocessing device 4 may provide the offset-corrected actuation positionto the application processor 11, for example.

The handheld electronic device 1 may be operative as a handheldcommunication device, e.g. a cellular telephone, a personal digitalassistant, a handheld computer or similar. The handheld electronicdevice 1 may include components for voice communication, which mayinclude a microphone 6, a speaker 7, and a wireless communicationinterface 9 for communication with a wireless communication network. Inaddition to the input interface, the handheld electronic device 1 mayhave separate hard keys 8, such as function and/or control keys, whichmay be supported on a housing 10 of the electronic device 1. Theapplication processor 11 may perform an operation which depends on theoffset-corrected actuation location, such as by retrieving data from amemory 5, determining an alphanumerical input, or performing one ofplural voice or data communication operations which is selected as afunction of the offset-corrected actuation location.

The electronic device may also comprise a force sensor 13. The forcesensor 13 may be operative to determine a force with which a finger ormultiple fingers is/are pressed against the input surface 3. Theapplication processor 11 may be operative to perform different functionsdepending on the force that is sensed. The force thus acts as anadditional input coordinate, sometimes also referred to as“z-coordinate” for actuation operations. An offset correction whichdepends on finger angle may be performed for this z-coordinate, i.e.,the force.

With reference to FIG. 3 to FIG. 16, the configuration and operation ofinput interfaces of electronic devices of embodiments will be explainedin more detail.

FIG. 3 is a perspective view illustrating a portion of the input surface21 of the electronic device. FIG. 4 is a cross-sectional view in a planeperpendicular to the input surface 21.

A finger 22 acts as an input member. The procedure of determining anoffset-corrected actuation position may be triggered when a contactbetween the finger 22 and the input surface 21 is detected. When theuser pushes the finger 22 against the input surface 21, the finger 22has a generally straight axis 24. The axis 24 extends at an angle 23relative to the input surface 21. This angle 23 is the “finger angle” 23which quantifies how the finger 22 is directed towards the input surface23. The finger angle 23 may also be determined as 90° minus the anglebetween the axis 24 and the normal 26 of the input surface. With thelower surface of the finger 22 extending generally parallel to the axis24, the finger angle 23 may also be determined as the angle between alower surface of the finger 22 and the input surface 21.

It has been found that the discrepancy between where a user thinks hehas pressed onto the input surface 21 and the sensed actuation positionvaries with finger angle. Electronic devices of embodiments at leastpartially compensate for this discrepancy by adding an offset to thesensed actuation position. The offset depends on the finger angle. Aswill be described in more detail below, the finger angle is determinedusing the proximity-sensitive touch sensor array.

FIG. 3 also illustrates the quantity referred to as “finger orientation”of the finger 22, which defines the direction of the finger 22 relativeto the coordinate axes of the input surface 21. The finger orientationis defined by the direction of the line 25 along which a projection ofthe finger 22 onto the input surface 21 extends. As will be described inmore detail below, the processing device may determine both the fingerangle 23 and the finger orientation from self-capacitance measurementsand/or mutual capacitance measurements of rows and columns of acapacitive touch sensor array. The processing device may determine amagnitude of the offset that is added to the sensed actuation positionas a function of the finger angle 23 and independently of the directionof the line 25 along which the projection of the finger 22 onto theinput surface 21 extends. The processing device may determine thedirection of the offset that is added to the sensed actuation positionsuch that it corresponds to the direction of the line 25 along which theprojection of the finger 22 onto the input surface 21 extends. Thedirection of the offset may be independent of the finger angle 23. Theoffset 34 may be such that it has a magnitude that depends on the fingerangle and that it is directed along the projection line 25 of the finger22 in a direction away from the finger tip.

FIG. 5 illustrates how the processing device determines theoffset-corrected actuation position. The finger contacts the inputsurface 21 in a fingerprint area 31. The actuation position 32 may bedetermined from the fingerprint area 31, e.g. by determining a center ofgravity of the area 31 or the position at which the finger causes themost pronounced capacitance change. The offset-corrected actuationposition 33 is determined by adding an offset 34 to the actuationposition 32. The offset 34 has a magnitude which depends on the fingerangle 23. The processing device may derive the magnitude of the offsetfrom the finger angle by querying a look-up-table, by evaluating afunction which defines the magnitude of the offset in dependence on thefinger angle and/or by interpolating between values defined in a look-uptable. The magnitude of the offset is set such that it corresponds to orat least approximates the discrepancy between where the user thinks hehas touched the input surface 21 and the sensed actuation position 22,respectively as a function of finger angle.

The direction of the offset 34 depends on the line 25 along which theprojection of the finger onto the input surface 21 extends. Theprocessing device may determine an x-shift 35 and a y-shift 36 tocompute the offset-corrected actuation position. For illustration ratherthan limitation, an angle 37 between the line 25 and one of thecoordinate axes of the input surface may be determined. The x-shift 35may be computed by multiplying the magnitude of the offset 34 by thecosine of the angle 37. The y-shift 36 may be computed by multiplyingthe magnitude of the offset 34 by the sine of the angle 37. A widevariety of other techniques may be used to derive the magnitude anddirection of the offset 34 from the data captured using the touch sensorarray. For illustration, data captured using a capacitive touch sensorarray may be directly compared to a plurality of data sets to deriveboth the magnitude of the offset 34 and the direction of the offset 34.

The finger angle may also be used for additional processing steps. Forillustration, an expected fingerprint may be predicted using the fingerangle. The expected fingerprint may be matched to the sensed fingerprint31. The finger angle may in particular be used to account for fingerangle dependent changes in the fingerprint. This may be useful whendetermining a force magnitude from the fingerprint, for example, becausethe fingerprint generally depends on the finger angle and the force withwhich the finger is pressed against the input surface.

FIG. 6 is a cross-sectional view in a plane perpendicular to the inputsurface 21 when the finger is directed towards the input surface 21 atanother finger angle 27. FIG. 7 is a plan view which illustrates thatthe offset-corrected actuation position 43 is determined by adding anoffset 44 to the sensed actuation position 42. The sensed actuationposition 42 may be derived from a fingerprint area 41 in which thefinger contacts the input surface 21. The magnitude of the offset 44 isdifferent from the magnitude of the offset 34 illustrated in FIG. 5.This reflects that the discrepancy between where the user thinks he haspressed against the input surface 21 and the actual actuation positionvaries with finger angle, and that the offset is accordingly selected asa function of finger angle to better compensate this discrepancy. Themagnitude of the offset may decrease as the finger angle increases from0° to 90°.

The processing device of the electronic device of an embodimentdetermines the finger angle from the data captured using a touch sensorarray. As will be explained in more detail with reference to FIG. 8 toFIG. 16, the processing device may derive from the data captured usingthe touch sensor array how the distance between the finger and the inputsurface 21, measured perpendicular to the input surface 21, varies as afunction of location. This distance variation defines the finger angle.FIG. 6 illustrates distances 28, 29 between the finger and the inputsurface 21. These distances 28, 29 may be determined from the datacaptured using a capacitive touch sensor array, for example. Thedistances 28, 29 between the finger and the input surface 21 may inparticular be determined by performing row scans and columns scans for acapacitive touch sensor array in which the self-capacitances of rows andcolumns of the capacitive touch sensor array are determined. The spatialvariation of self capacitances can be used to determine the fingerangle.

FIG. 8 is a flow chart of a method of an embodiment. The method may beperformed by an electronic device of an embodiment.

At 51, data is captured using a proximity-sensitive touch sensor array.The proximity-sensitive touch sensor array may be a capacitive touchsensor array. The capacitive touch sensor array may comprise aconductive pattern which has a plurality of rows and a plurality ofcolumns. Self-capacitance measurements and/or mutual capacitancemeasurements may be performed to determine the finger angle.Alternatively or additionally, other sensing techniques may be used tocapture the data from which the finger angle and actuation position aredetermined. For illustration, the proximity-sensitive touch sensor arraymay be an optic touch sensor, an IR sensing sensor array, an electricalfield sensor array, a sonar sensor array, an ultra sound sensor arrayand/or Doppler sensor array configured for proximity and touch sensing.

At 52, the finger angle is determined. The data captured using theproximity-sensitive touch sensor array indicate a distance variationbetween finger and input surface as a function of position, i.e. in aspatially resolved manner. This information may be used to establish thefinger angle. A spatial gradient of self-capacitances and/or mutualcapacitances may be determined to derive the finger angle. Alternativelyor additionally, the data captured using the proximity sensitive touchsensor array may be compared to a plurality of pre-defined data sets,which are respectively associated with a pre-defined finger angle.Matching of the captured data to the pre-defined data sets may beperformed to determine the finger angle. To determine the finger anglewith even higher resolution, an interpolation between the pre-definedfinger angles may be performed, depending on how well the captured datamatches the various pre-defined data sets.

At 53, the offset may be determined. The position offset may bedetermined by performing a look-up operation. The respective look-uptable may specify pre-defined offset magnitudes as a function of fingerangle for plural pre-defined finger angles. Interpolation techniques maybe used to determine the offset magnitude for the finger angledetermined at 52, using a finite set of pre-defined offset magnitudesstored in a look-up table. Alternatively or additionally, the processingdevice may evaluate a function which depends on the finger angle, usingthe finger angle determined at 52.

The data captured at 51 may comprise self-capacitances of rows andcolumns of a capacitive touch sensor array. Self-capacitancemeasurements offer the advantage of having a large detection range forproximity sensing. This facilitates a reliable determination of thefinger angle.

FIG. 9 is a flow chart of a method of an embodiment. The method may beperformed by an electronic device of an embodiment. In the method ofFIG. 9, both self capacitance measurements 55 and mutual capacitancemeasurements 56 are performed. The finger angle is determined at 52based on both the self-capacitances of rows and columns and on mutualcapacitances between rows and columns of the capacitive touch sensorarray. The higher spatial resolution of mutual capacitance measurementsmay be utilized to identify a best match between the captured data andpre-defined finger angles. A weighting may be performed based on thedata captured in row and columns scans of the self-capacitancemeasurements 55 and/or based on the data captured in the mutualcapacitance scan at 56, so as to derive the finger angle with highaccuracy.

The processing device may perform any one of various processingtechniques to determine the finger angle from data captured using thetouch sensor array.

In one implementation, the processing device may match the data capturedwith the touch sensor array to pre-defined data sets which are stored inthe electronic device and which correspond to various pre-defined fingerangles.

Alternatively or additionally, characteristics of the data capturedusing the touch sensor array as a function of location may be used todetermine the finger angle. For illustration, the gradient incapacitance and/or the length over which the capacitance variessignificantly may be used to determine the finger angle.

FIG. 10, FIG. 11 and FIG. 12 illustrate exemplary raw data capturedusing a proximity-sensitive touch sensor array, from which the fingerangle and the offset magnitude may be determined. Data as illustrated inFIG. 10, FIG. 11 and FIG. 12 may be obtained when performing a row scanin which self-capacitances of different rows of a capacitive touchsensor array are measured or when performing a column scan in whichself-capacitances of different columns of the capacitive touch sensorarray are measured. Accordingly, the captured data may represent selfcapacitances of different rows or different columns, respectively, of acapacitive touch sensor array.

FIG. 10 illustrates the data obtained when the finger is directedtowards the input surface at a small finger angle. There is a pronouncedincrease in self-capacitance in the row or column where the finger tipabuts on the input surface. The sensed self-capacitance decreases with asmall gradient 61 in the subsequent rows or columns. This indicates thatthe finger angle between the finger and the input surface is small,causing the distance between finger and input surface to increase slowlyas a function of position. The slope or gradient 61 may be used todetermine the finger angle.

FIG. 11 illustrates the data obtained when the finger is directedtowards the input surface at a greater finger angle. Again, there is apronounced increase in self-capacitance in the row or column where thefinger tip is located. The sensed self-capacitance decreases with agreater gradient 62 in the subsequent rows or columns. This indicatesthat the finger angle between the finger and the input surface isgreater than in the situation illustrated in FIG. 10, causing thedistance between finger and input surface to increase more rapidly as afunction of position.

FIG. 12 illustrates the data obtained when the finger is directedtowards the input surface at an even greater finger angle. Again, thereis a pronounced increase in self-capacitance in the row or column atwhich the finger tip is located. The sensed self-capacitance decreaseswith a greater gradient 63 in the subsequent rows or columns. Thisindicates that the finger angle between the finger and the input surfaceis greater than in the situations illustrated in FIG. 10 and in FIG. 11,causing the distance between finger and input surface to increase evenmore rapidly as a function of position.

Based on the data captured using the capacitive touch sensor array, thefinger angle may be determined. A look-up operation may be performedand/or a function may be evaluated which depends on the finger angle, tothereby determine the offset which is added to the sensed actuationposition. For illustration, for a finger angle of 15°, the offset whichis added to the sensed actuation position may have a first magnitude,such as 10 pixels. For a greater finger angle, e.g. a finger angle of25°, the offset which is added to the sensed actuation position may havea second magnitude which is less than the first magnitude, such as 7pixels. For even greater finger angle, e.g. a finger angle of 45°, theoffset which is added to the sensed actuation position may have a thirdmagnitude which is less than the second magnitude, such as 4 pixels.Generally, the offset which is added to the sensed actuation position toat least partially compensate for finger-angle dependent offset effectsmay have a magnitude which is a decreasing function of finger angle.

An offset correction which depends on finger angle may be performed notonly for the x and y coordinates of the actuation position, but mayadditionally or alternatively for a z coordinate of an input action. Thez coordinate may correspond to a force applied onto the input surface bya finger or by multiple fingers.

FIG. 13 is a schematic plan view of a touch sensor array 71 which may beused in electronic devices of embodiments. The touch sensor array 71comprises a conductive pattern which may be applied on a carrier 70. Thecarrier 70 may be a window overlaid over a display of the electronicdevice or a separate panel interposed between the display and thewindow. The conductive pattern has a plurality of columns 81-85 and aplurality of rows 86-88. A flexible printed circuit board (PCB) 74 maybe attached to the carrier 70. A controller 75 may be provided on thePCB 74 and may be connected to the conductive pattern by conductivetraces 72, 73. The controller 75 may determine the finger angle andactuation position based on capacitance data sensed using the conductivepattern, and may provide the offset-corrected actuation position to theapplication processor of the electronic device. A connector 76 on thePCB 74 may act as interface between the controller 75 and theapplication processor.

The controller 75 may perform row scans to determine self-capacitancesof the various rows 86-88 of the conductive pattern. The controller 75may perform columns scans to determine self-capacitances of the variouscolumns 81-85 of the conductive pattern. The controller 75 may determinethe finger angle based on the data obtained in the row scans and columnscans, as explained with reference to FIG. 10 to FIG. 12.

The controller 75 may also be operative to measure mutual capacitancesbetween rows and columns. For illustrations, the mutual capacitancesbetween various pairs of rows and columns of the conductive pattern maybe measured to determine the finger angle. The mutual capacitances maybe measured to determine the actuation position.

The determination of the finger angle may be triggered by an inputaction. For illustration, the processing device may be triggered todetermine the finger angle and to establish the offset-correctedactuation position when a contact between finger and input surface isdetected. The offset-corrected actuation position may be used by theelectronic device to determine which one of plural different operationsis to be performed.

FIG. 14 is a flow chart of a method 90 of an embodiment. The method maybe performed by an electronic device of an embodiment.

At 91, it is determined whether a touch is detected. This determinationmay be made based on data captured by the touch sensor array.Alternatively or additionally, other sensors may be used to detect atouch. For illustration, the electronic device may have a force sensorwhich facilitates discrimination of touch and non-touch events.

When a touch is detected, at 92 the coordinates of the actuationposition are determined. The actuation position may be determined fromdata captured in self-capacitance and/or mutual capacitancemeasurements. The actuation position may also be determined using afinger angle. At 93, the finger angle is determined while the fingercontacts the input surface. The finger angle may be derived from dataacquired in self-capacitance measurements, e.g. in row scans and columnscans.

At 94, the offset-corrected actuation position is determined. An offsetmay be added to the actuation position. The offset may have a magnitudewhich depends on the finger angle. The offset may have a magnitude whichis a decreasing function as the finger angle increases from a minimumangle to a maximum angle.

At 95, the electronic device performs an operation which depends on theoffset-corrected actuation location. For illustration, when a keypad isdisplayed to allow the user to input alphanumerical data, a key actuatedby the user may be selected as a function of the offset-correctedactuation location. For further illustration, when differentcall-related actions are offered to the user, the action which isexecuted may be selected as a function of the offset-corrected actuationlocation.

For a multi-touch input operation, steps 92-94 may be performed for eachone of the various fingers which touches the input surface.

FIG. 15 and FIG. 16 illustrate data 96, 97 captured using a capacitivetouch sensor array, which shows that this data allows plural fingerangles to be discriminated. The data is captured using a dummy fingerwith a finger orientation along a central row of the display anddirected at various finger angles. FIG. 15 shows the self-capacitancedata 96 obtained in a row scan for various finger angles. The selfcapacitance has a peak at the rows where the dummy finger is located.

FIG. 16 shows the self-capacitance data 97 obtained in a column scan forvarious finger angles. For a finger directed towards the input surfaceat a smaller finger angle of 15° or 25° degrees, for example, theself-capacitance values for the columns indicated in region 99 still hasfairly large values, indicating that the finger angle is small and thefinger is close to the input surface even in those columns. For a fingerdirected towards the input surface at a finger angle of 65° or 90°degrees, the self-capacitance decreases rapidly and is small for thecolumns which correspond to region 99. For an intermediate finger angleof 45°, the self-capacitance decreases less rapidly in the region 99than for the larger finger angles of 65° or 90° degrees, respectively.The capacitance data obtained in self-capacitance measurements and/ormutual capacitance allows the processing device to derive the fingerangle.

FIG. 17 is a flow chart of a method of another embodiment. As previouslyindicated, a finger-angle dependent offset correction may not only beperformed for the x and y coordinates of an actuation position, but mayadditionally or alternatively be performed also for the so-called zcoordinate. Frequently, the force with which a user presses a finger ormultiple fingers against the input surface is used as a z coordinate,which allows a user to activate different functions depending on howstrongly he/she presses the finger(s) against the input surface.

At 101, data are captured. The data may comprise proximity data thatallows the finger angle to be determined. The data comprise az-coordinate of an actuation position. The z-coordinate may correspondto a force sensor value provided by a force sensor. The z-coordinate mayquantify the force with which the finger(s) is or are pressed againstthe input surface.

At 102, the finger angle is determined. The finger angle may bedetermined using any one of the techniques described with reference toFIG. 1 to FIG. 16.

At 103, an offset-corrected z-coordinate value is determined. Theprocessing device may determine an offset for the z-coordinate as afunction of finger angle and may add the offset to the sensedz-coordinate. An application processor of the electronic device mayperform an operation which depends on the offset-corrected z-coordinatevalue. Thereby, offset problems may be mitigated also for force sensing.As described with reference to FIG. 1 to FIG. 16, the offset may bedetermined by querying table(s) and/or by evaluating a function for thespecific determined finger angle.

Various techniques may be used to establish an offset that is added to asensed coordinate using the finger angle. In some implementations,look-up tables may be used. Alternatively or additionally, amathematical function may be evaluated which depends on finger angle.Still further, interpolation techniques may be used in either case tocompensate offset problems with even greater precision. The tablesand/or functions which are used to determine the offset when the fingerangle is known may be pre-defined data, which may be generated bysampling a large number of input operations performed by various users,for example. Alternatively or additionally, the electronic device of anyembodiment may also be configured to perform a procedure in which thetable(s) and/or function(s) used for offset correction may be determinedfor a specific user.

FIG. 18 is a flow chart of such a procedure which may be performed by anelectronic device of any embodiment. At 111, a training phase isexecuted in which the electronic device automatically determines offsetsbetween intended and actual actuation positions. The offsets aredetermined for various finger angles. The electronic device may output amessage or other graphical data requesting the user to press his fingeragainst a target location. The actual actuation position and fingerangle may be recorded. The offset between actual actuation position andtarget location may be recorded in association with the respectivefinger angle. To generate tables or functions that do not only depend onfinger angle, but also depend on the finger which is pressed against theinput surface or on the device orientation, such data may be recordedfor input actions performed with various fingers and/or for differentdevice orientations.

At 112, the offsets and associated finger angles determined at 111 areused to generate a table and/or function which may subsequently be usedfor determining an offset when the finger angle is known. When table(s)are used by the processing device to determine an offset for a givenfinger angle, the data captured at 111 may be written into the table(s).When function(s) are evaluated by the processing device to determine anoffset for a given finger angle, parameters of the functions (e.g.coefficients of a polynomial) may be set so as to fit the data capturedat 111. These steps may be performed automatically by a processor of theelectronic device.

The table(s) and/or function(s) determined at 112 may be stored in theelectronic device for subsequent use in performing offset-correction.

At 113, the table(s) and/or function(s) determined at 112 may optionallybe shared with at least one further electronic device according to anembodiment. This may be beneficial in particular when one user usesdifferent electronic devices or starts using a new electronic deviceafter having trained another electronic device in accordance with steps111 and 112. The table(s) and/or function(s) determined at 112 may betransferred to the other electronic device, e.g. using a near fieldcommunication technique or via a wireless communication networks.

FIG. 19 is a block diagram representation of a communication system. Thecommunication system has electronic devices 1, 121 which respectivelyare configured as electronic devices according to an embodiment. Theelectronic device 1 may perform the procedure explained with referenceto FIG. 18 to automatically generate the data structures which aresubsequently used in finger angle dependent offset correction. Theelectronic device 1 may transfer these data structures to the otherelectronic device 121. This may be done directly, e.g. using Bluetoothcommunication. Alternatively, the electronic device 1 may transfer thedata structures which are subsequently used in offset correction to aserver 122 interfaced with a mobile communication network. The otherelectronic device 121 may retrieve the data structures from the server122.

The data structures which are used for offset correction, e.g. table(s)and/or functions which allow an offset to be determined as a function offinger angle, may have various formats. For illustration, offsets may bespecified in units of pixels. Alternatively, offsets may be specified interms of relative magnitudes measured with respect to dimensions of theinput surface. For illustration, a table may store numerical valueswhich quantify offsets in units of pixels or in units of a givenpercentile (e.g. 1%) of a display width or display height.

While handheld electronic devices and methods of processing useractuation of an input interface have been described with reference tothe drawings, modifications and alterations may be implemented infurther embodiments. For illustration, input interfaces configured asdescribed herein may not only be used in handheld communication devices,but may also be used in a wide variety of other electronic deviceshaving a proximity-sensitive touch sensor array.

The techniques described herein may be applied to mitigate offsetproblems in multi-touch input operations. In this case, the fingerangles for multiple fingers may be determined. An offset-correctedactuation position may be determined for each one of the multiplefingers touching the input surface, which is respectively determinedusing the finger angle for the respective finger. The techniquesdescribed herein may not only be used to mitigate finger angle dependentoffsets for touch actions, but may also be used to mitigate such offsetproblems for non-touch actuation of a user interface.

While certain techniques for determining the finger angle and/or fordetermining a magnitude of a position offset have been described, othertechniques may be also be used. For illustration, the finger angle maybe determined using self-capacitance measurements, mutual-capacitancemeasurements or a combination thereof. For further illustration, themagnitude of the offset which is added to the sensed actuation positionmay be determined using look-up tables, by interpolating betweenpre-defined finger angle values in dependence on the measured data, byevaluating a function which depends on the finger angle, or by using acombination of such techniques.

The touch sensor array of each embodiment may be used in combinationwith a display to thereby provide a graphical user interface. Thegraphical user interface may comprise a conventional display, astereoscopic display or an autostereoscopic display, for example.

In each one of the embodiments, additional processing may be performedto compensate offset problems. For illustration, the processing devicemay be configured to at least partially compensate fat finger offsets,in addition to determining the offset which is caused by the differentfinger angles, or the “fly in” directions, of the finger.

Although the invention has been shown and described with respect tocertain preferred embodiments, equivalents and modifications will occurto others skilled in the art upon reading and understanding thespecification. The present invention includes all such equivalents andmodifications and is limited only by the scope of the appended claims.

What is claimed is:
 1. An electronic device, comprising: aproximity-sensitive touch sensor array which extends along an inputsurface of the electronic device; a force sensor configured to determinea force with which a finger is pressed against the input surface ormultiple fingers are pressed against the input surface; and a processingdevice coupled to the touch sensor array, the processing device beingconfigured to: process the data captured by the touch sensor array todetermine a finger angle at which the finger is directed towards theinput surface and an actuation position on the input surface, determinea position offset for the actuation position on the input surface as afunction of the finger angle, establish an offset-corrected actuationposition as a function of the actuation position and the positionoffset, and determine a force offset as a function of the finger angle,derive an offset-corrected force value from an output of the forcesensor and the force offset.
 2. The electronic device of claim 1,wherein the processing device is configured to determine a variation indistance of the finger from the input surface in a spatially resolvedmanner and to derive the finger angle from the variation in distance. 3.The electronic device of claim 1, wherein the touch sensor arraycomprises a conductive pattern for capacitive touch and proximitysensing, and the processing device is configured to determine the fingerangle from sensed capacitance values.
 4. The electronic device of claim3, wherein the conductive pattern comprises a plurality of rows and aplurality of columns, and wherein the processing device is configured todetermine the finger angle based on self-capacitance measurements of theplurality of rows and self-capacitance measurements of the plurality ofcolumns.
 5. The electronic device of claim 4, wherein the processingdevice is configured to determine the actuation position based on mutualcapacitance measurements between rows and columns of the conductivepattern.
 6. The electronic device of claim 4, wherein the processingdevice is configured to derive the finger angle from a gradient ofself-capacitances of rows and a gradient of self-capacitances ofcolumns.
 7. The electronic device of claim 4, wherein the processingdevice is configured to carry out a row scan to perform theself-capacitance measurements for the plurality of rows and a columnscan to perform the self-capacitance measurements for the plurality ofcolumns, and to derive the finger angle from data obtained in the rowscan and data obtained in the column scan.
 8. The electronic device ofclaim 4, wherein the processing device is a controller coupled to theconductive pattern and configured to provide the offset-correctedactuation position to an application processor of the electronic device.9. The electronic device of claim 4, wherein the processing device isconfigured to add an offset to the actuation position on the inputsurface or to subtract an offset from the actuation position on theinput surface to establish the offset-corrected actuation position,wherein the processing device is configured to establish a magnitude ofthe offset as a function of the finger angle.
 10. The electronic deviceof claim 9, wherein the processing device is further configured toderive a finger orientation from the data captured by the touch sensorarray, the finger orientation defining a direction of a projection ofthe finger onto the input surface, and to establish a direction of theoffset as a function of the finger orientation.
 11. The electronicdevice of claim 4, wherein the actuation position comprises az-coordinate which depends on the force applied by the finger onto theinput surface, wherein the processing device is configured to establishan offset-corrected z-coordinate as a function of the z-coordinate ofthe actuation position and the finger angle.
 12. The electronic deviceof claim 4, further comprising: an application processor coupled to theprocessing device to receive the offset-corrected actuation position,the application processor being configured to perform an operation whichis selected in dependence on the offset-corrected actuation position.13. The electronic device of claim 4, wherein the processing device isconfigured to detect a multi-touch input operation in which at least onefurther finger touches the input surface at at least one furtheractuation position, to determine at least one further finger angle atwhich the at least one further finger is directed towards the inputsurface, and to establish at least one further offset-correctedactuation position as a function of the at least one further actuationposition and the at least one further finger angle.
 14. The electronicdevice of claim 1, wherein the processing device is configured to derivea direction of the force sensed by the force sensor based on the fingerangle.
 15. The electronic device of claim 1, wherein the electronicdevice is configured to perform an operation in response to theoffset-corrected force value.
 16. A method of processing a useractuation of an input surface of an electronic device, the methodcomprising: capturing data using a proximity-sensitive touch sensorarray which extends along the input surface of the electronic device;processing the data captured by the touch sensor array to determine afinger angle at which a finger is directed towards the input surface andan actuation position on the input surface; determining a positionoffset for the actuation position on the input surface as a function ofthe finger angle, establishing an offset-corrected actuation position asa function of the actuation position and the position offset; andsensing, by a force sensor, a force with which a finger is pressedagainst the input surface or multiple fingers are pressed against theinput surface; determining a force offset as a function of the fingerangle, deriving an offset-corrected force value from an output of theforce sensor and the force offset.